Samples of bodily fluids, such as blood and the like, derived from patients usually include particulate matter suspended in a liquid medium known as a supernatant. The suspended particulate matter may, for example, include cellular material, cells, and bacteria. When it is desired to closely analyze such particulate matter (hereafter "particles") it is usually necessary to deposit those particles upon suitable deposition surfaces, as microscope slides, so that further examination may occur. The deposition of the particles on the slide is usually accomplished through the use of a centrifuge apparatus. Rotation of the centrifuge rotor causes the particles to move under the influence of a centrifugal force field and impact, or sediment, upon the slide. The supernatant is also impelled by the force field toward the slide. However, the supernatant must be removed so that the sedimented cells can remain in position on the slide.
Devices such as that available from Shandon-Elliot and sold under the name "Cytospin" have been used to concentrate particles on slides. In this device, filter paper has been used to withdraw excess supernatant from the surface of the slide. It has been observed, however, that the use of filter paper for such a purpose has the tendency to absorb or to draw cells from the slide's surface. This is perceived as disadvantageous.
The problems attendant with the use of filter paper as the supernatant absorbing medium are believed to be overcome by a device described and claimed in copending application Ser. No. 15,911, filed Feb. 28, 1979 and in copending application Ser. No. 131,678, filed Mar. 19, 1980, both assigned to the assignee of the instant invention. Such a device, which is manufactured and sold by Sorvall Division of E. I. du Pont de Nemours and Company utilizes removable chamber blocks each of which includes an inlet channel into which a sample suspension is introduced and an outlet channel through which the supernatant and particles travel under the influence of a centrifugal force toward the slide surface. A conduit is formed within the chamber block with one end of the conduit being disposed in the vicinity of the outlet orifice and the surface of the slide. The other end of the conduit is communicable with an external suction device. When a suction is applied to the conduit excess supernatant is withdrawn from the surface of the slide, thus permitting the sedimented cells to remain in position on the slide surface.
Since in some instances the amount of the sample is limited, it is believed desirable to provide an arrangement whereby the supernatant may be withdrawn without commingling that supernatant with supernatant used to support particles from other samples. Thus, that portion of the specimen particles not deposited on the slide may advantageously be individually retrieved and held for further use. It is also believed desirable to provide a centrifuge rotor arrangement whereby samples, which may be radioactively tagged or otherwise treated, may be sedimented and the supernatant which supports such particles segregated. Such an arrangement would isolate the supernatant which supported the treated particles, thus avoiding contamination of common external collection bottles or of the centrifuge.